"FOUND IF A FAILED DEVICE IS CONNECTED TO PIXHAWK THE USB WILL NOT LOAD IN MISSION PLANNER.  COULD BE ANY DEVICE, EXAMPLE IF THE APM POWER MODULE IS NOT POWERED ON IT WILL SHOW UP AS A FAILED DEVICE AND PREVENT MISSION PLANNER FROM CONNECTING OVER…"

"CONFIRM:  
I HAD SAME PROBLEM,
PIXHAWK USB COM PORT FAILS IN DEVICE MANAGER WHEN CONNECTING & DOESNT SHOW.  
FOUND THIS POST http://diydrones.com/forum/topics/pixhawk-and-mavlink-problem 
I UNPLUGGED THE "UBLOX COMPASS ( SDA/SDL 3V3 ) CONNECTOR".…"

"CONFIRM:  
I HAD SAME PROBLEM,
PIXHAWK USB COM PORT FAILS IN DEVICE MANAGER WHEN CONNECTING & DOESNT SHOW.  
FOUND YOUR POST & CORRECT!
I UNPLUGGED THE "UBLOX COMPASS ( SDA/SDL 3V3 ) CONNECTOR".
AND THE PIXHAWK COM PORT SHOWED UP!  

SUGGEST I HAD…"

"TEENSY MAVLINK FRSKY SPORT FAILING FLVSS WHILE LOOPING ABSENT POWERMODULE: 
FOUND THIS FORUM ENTRY ABOVE & SUCCESS. 

1.  WITH TEENSY DAISYCHAINED TO FLVSS & WITHOUT APM POWER MODULE TO READ VOLTAGES
1A.  FAIL:  VERSION MavLink_FrSkySPort_1.3.zip…"

"ENQUIRY SOFTWARE:
1.  ? FAILED TEENSY LOADER WITH MINIPRO. 
1A.  AFTER VERIFY/COMPILE EDITOR SAYS: 
OPENING TEENSY LOADER
TEENSY REBOOT
PRESS RESET BUTTON ON TEENSY TO UPLOAD SKETCH
AUTO REBOOT IF TEENSY RUNNING PREVIOUS SKETCH

1B:  ?HOW TO SUCCESS…"

"ENQUIRY AFTER VERIFY/COMPILE: 
1.  PLEASE PRESS THE RESET BUTTON ON TEENSY TO UPLOAD SKETCH. 

ON MY MINI PRO I PRESS THE RESET BUTTON & THE TEENSY LOADER DOES NOTHING WHILE MINIPRO BLINKS. 

SUGGESTIONS?"

"ENQUIRY CONFIGURATION:
1.  PIXHAWK
2.  ARDUINO MINI PRO
3.  X8R & TARANIS

ENQUIRY SOFTWARE: 
1.  ? PIN 9 SUPPORTED IN MavLink_FrSkySPort_1.3.zip ?  

ENQUIRY HARDWARE:
1.  ? SUCCESS WITH PIXHAWK OR ONLY APM ?

A.  SUCCESS FOUND YOUR ARDUINO…"

"MY CONFIGURATION: 
1.  PASSED THROTTLE @ MODE STABILIZE/ACRO/MANUAL
2.  FAIL THROTTLE @ MODE CIRCLE/CRUISE/RTL
3.  ENABLE THROTTLE_SUPP_MAN
3A.  SUCCESS THROTTLE @ MODE CIRCLE/CRUISE/RTL"